The JR blood group system (ISBT 032): molecular characterization of three new null alleles.

Background: Jr(a) (ISBT 901005) is a high-prevalence antigen unassigned to a blood group system. People lacking this antigen have been found in all populations studied but most commonly in Asians. Two recent reports established that ABCG2-null alleles encode the Jr(a-) phenotype and these studies provided the impetus to study other Jr(a-) individuals.

Study Design And Methods: Blood samples were part of our rare donor-patient collection. DNA was isolated and analyzed by standard techniques.

Results: In samples from 13 Jr(a-) study subjects, we found six alleles with nonsense nucleotide changes, three (c.784T, c.1591T, and c.337T) were novel. Twelve of the samples were homozygous for nonsense single-nucleotide polymorphisms (SNPs): eight were c.376T, two were c.706T, one was c.784T, and one was c.1591T. Each of these alleles predicts a truncated ABCG2 product, Gln126Stop, Arg236Stop, Gly262Stop, and Gln531Stop, respectively. One study subject was heterozygous for two nonsense SNPs: c.337C/T (Arg113Stop) and c.736C/T (Arg246Stop).

Conclusions: Jr(a) is the sole antigen in the newly established JR blood group system (ISBT 032001). The previous ISBT designation (901005) is now obsolete. Since ABCG2null alleles define the Jr(a-) phenotype, an explanation for why no antithetical low-prevalence antigen to Jr(a) has been found, and also why anti-Jr(a) made by people with any of these JRnull alleles are mutually compatible has been determined. Based on our findings DNA-based genotyping can be developed to replace the serologic methods that are currently used to identify Jr(a-) blood donors.